Quickest way to get FIA International C license to compete in BTCC and ETCC?

Hello everyone,
What would you recommend as best and quickest way to get FIA International C license?
In the past I think it was enough to complete 16 National B races on 6 different tracks to go from a Nat B licence to an Int C.

Nat. B to Nat. A - get 6 signatures from club level events, 1 of which can be for marshalling.

Nat. A to Int. D - the holder of a National A can upgrade to International D without any further criteria, just the cost of the upgrade (the difference between the two plus an upgrade fee)

Nat. A or Int. D to Int. C. - get Signatures from: 3 National A races OR 2 National ‘A’ plus 2 National ‘B’ or Clubman Races OR 6 National ‘B’ or Clubman Races. All from three different venues.

Int C to Int B and Int. B to Int. A. - compete satisfactorily in at least 10 national races or international races within the previous 2 years, and if you've finished in the top 5 of those races and finished within the top 5 of a suitable important championship, then you can get Int. A rather than Int. B.

Int. A to FIA Super Licence - accumulate at least 40 qualifying points within three years. Winning GP2, Indycar, F3 European series gives you 40 points. Winning national F4 gives you 12 points.